The present invention relates to a method of efficiently grinding a ferrule used for an inclined PC connector by which inclined grinding surfaces of optical fibers are connected to each other.
As an optical connector used in an optical communication, or the like, an inclined PC (Physical Contact) connector is used for the purpose of reducing connection loss and beam reflection in the connecting section. In the inclined PC connector, an end face of an optical fiber is ground together with a ferrule to provide a convex spherical surface inclined with respect to a plane orthogonal to an axis of the optical fiber. As shown in FIG. 4, the ferrule 100 prior to the grinding process has a basically cylindrical configuration, which has a flange 110 at its rear end portion and a through-hole 111 for insertion and fixing of the optical fiber at its center. The leading end face of the ferrule is perpendicular to the through-hole 111.
This ferrule 100 is subjected to the grinding process as shown in FIGS. 5A-D. That is, an optical fiber 12 is held on the ferrule 100 having a truncated-cone like leading end portion defining the leading end face perpendicular to the axis, and then the leading end face is ground to provide a convex spherical surface, refer to FIG. 5A. After the eccentric direction of the core of the optical fiber 12 is inspected, the ferrule 100 is mounted to a jig in such a state that its leading end face is inclined, for instance, at 8.degree. with respect to the surface 120a of the grinding abrasive wheel 120 (refer to FIG. 5B), and the leading end face is ground to provide an inclined planar face, (refer to FIG. 5C). Although the expression of "cut" may be more appropriate, the terminology "grind" is used for convenience. Here, the core eccentric direction is set, for instance, so as to be at the front side of this drawing. Subsequently, the process advances to a step of grinding the leading end face to provide a convex spherical surface in the similar mounting state to the jig. By this, the inclined PC grinding is completed. The inclined spherical grinding can be performed similarly to the general convex spherical grinding with the exception of the mounting state in which the ferrule 100 is mounted incliningly, and as shown in FIG. 5D, it is performed such that the ferrule end face is swung with a grinding table base 121 rotated under a condition that the ferrule end face is depressed onto a grinding sheet 123 placed through an elastic member 122 on the grinding table base 121.
In the prior art, in order to finish the end face of the ferrule 100 to provide an inclined surface, (hereafter, this step is referred to as "cutting" when applicable), the end face of the ferrule 100, which is chucked in an inclined state, is depressed onto the surface 120a of the rotating abrasive wheel 120. That is, the ferrule 100 is held and fixed onto a chuck in a state that the axis of the ferrule 100 is inclined at a predetermined angle, for instance, 8.degree., with respect to the normal of the abrasive wheel surface 120a, and the abrasive wheel 120 is depressed onto the ferrule 100 while being rotated, thereby effecting the inclined planar grinding onto the end face of the ferrule 100.
As noted above, the inclined spherical grinding of the prior art is performed such that the end face of the ferrule, which has the cylindrical base portion and tapered, truncated-cone-like leading end portion, is subjected to the general spherical grinding, the inspection of the core eccentricity, and then the inclined planar grinding, and thereafter the inclined planar end portion is ground to provide a spherical surface.
The above-noted inclined spherical grinding method, however, suffers from a problem in that it requires a larger number of grinding steps in comparison to the general ferrule grinding methods. Further, in a case of the inclined spherical grinding, it is preferable to reduce a curvature eccentricity of the leading end spherical surface in comparison to the general ferrule since there arises the adverse effect due to the rotative variation of the ferrule in the connector connecting portion.